Unhealthy behaviors such as smoking, medication non-adherence, and lifestyle habits leading to obesity are major contributors to premature morbidity and mortality among the U.S. population. Participation rates in programs designed to improve these behaviors are often less than 10%. Considerable research has shown that lotteries that leverage the principle of anticipated regret are particularly effective at motivatin behavior change and increasing participation. These lotteries provide encouragement to perform a specified health behavior not only by offering a reward for successful participation, but also by fostering a sense of regret if a reward would have been won if only they had participated the day before. These approaches have been repeatedly successful in research settings, but the mechanisms to run these lotteries are not currently available in commercial settings. In this Phase I/Phase II Fast Track project, we will develop a scalable web-based application to run regret lotteries to improve participation in and outcomes from health improvement programs. The initial application will focus on smoking cessation program participation. Future modules will include weight loss, disease management, and medication adherence. Ultimately, the lottery tool will be available to employers, insurers, provider organizations, and product companies to improve participation in a wide range of health improvement programs, making the lottery approach readily accessible to small and large companies alike. Phase I Specific Aims: We will design, build, and test a web-based modular lottery software program to be used to increase health improvement program participation. We will: [1] design a web interface for administrators to customize program parameters and patients to track activity; [2] build cloud-based architecture to run a regret lottery; [3] create connectivity between this platform and email and SMS communications; and [4] test the product against technical standards and functionality with a 50-person, 30- day pilot. Phase II Specific Aims: We will expand and test a scalable, commercial regret-lottery with two stages of product testing: program scalability and improvement in program participation. We will: [1] enhance product functionality with a debit-card financial fulfillment solution; [2] run a 30-day pilot with 100 participants to test functionaities and refine user experience in commercial setting; [3] conduct a 6-month 438 participant pilot to measure smoking cessation participation rates with and without the lottery. With this project, we will bring the science of behavioral economics within reach of employers, insurers, provider organizations, and technology companies to improve health and health care for millions of Americans.